Quark matrix with improved taste characteristics (II)

ABSTRACT

A quark matrix having improved taste characteristics is suggested, which is obtainable by
     (a) subjecting raw milk to heat treatment, separating the cream,   (b) subjecting the skimmed milk such obtained to an ultrafiltration step, a microfiltration step, and/or a reverse osmosis step, producing a high-protein retentate R 1  and a high-lactose permeate P 1  in the process,   (c) enriching the retentate with an amount of lactose which corresponds to the amount that had been separated in the ultrafiltration step as permeate before,   (d) subjecting the enrichment product such obtained to heat treatment until denaturation sets in,   (e) fermenting the denaturation product such obtained by adding starter cultures and rennet, and   (f) adjusting the fermentation product such obtained to defined dry matter and protein contents.

FIELD OF THE INVENTION

The invention is in the field of dairy products and relates to a quark matrix having both an improved taste and a reduced sodium content, a process for its production, and foods containing the matrix.

STATE OF THE ART

For the production of quark or fresh cheese—these two terms will be used synonymously in the following—skimmed milk is typically subjected to heat treatment, denaturing the proteins contained therein.

As a result of the subsequent addition of lactic acid bacteria and rennet, the so-called coagulation (phase inversion) of the milk is performed. Casein is coagulated, forming the technically termed curd. After ripening (8 to 20 h), the curd is stirred. This process initiates the separation of whey, and the two phases are then separated in a separator. The liquid acid whey is processed otherwise, and the quark matrix is adjusted to the desired fat and protein contents by adding cream.

The technical methods of production are dominated by corresponding separation processes. By varying the conditions of separation and through technical modifications of the separators, it is currently possible to offer a variety of process configurations. With a protein content of the skimmed milk of 3.3 to 3.5% by weight, the use of skimmed milk is within the range of 4.10 to 4.15 kg skimmed milk per kilogramme of low-fat quark or fresh cheese to be produced (4.10 to 4.15 kg skimmed milk/kg low-fat quark), if the latter has a dry matter content of 18%. Thus, 3.10 to 3.15 kg acid whey are produced per kilogramme of low-fat quark (3.10 to 3.15 kg acid whey/kg low-fat quark). In this process, the protein content reaches a size of 12.6 to 12.8% by weight.

In addition to the methods of production that are characterised by separation, methods are known wherein the concentration of the fermented process milk is performed by ultrafiltration. For example, it is known from US 2003/0129275 A1 (LACT INNOVATION) that microfiltration steps and ultrafiltration steps may also be used for the production of cheese and quark. The application of microfiltration to skimmed milk for the production of cheese and whey protein products is described, for example, in US 2003/0077357 A1 (CORNELL RES FOUNDATION).

EP 1752046 A1 (TUCHENHAGEN) discloses a process for the production of fermented dairy products, wherein process milk is fermented, the fermentation product is subjected to a microfiltration step, and only the acidified retentate is processed.

In their paper, entitled “The pre-concentration of milk by nanofiltration in the production of Quark-type fresh cheeses”, MUCCHATTO ET AL describe the influence of using a previously nanofiltrated milk on the properties of quark that is produced from this nanofiltrated milk. Preliminary tests of the nanofiltration process were performed using aqueous solutions of NaCl, CaCl₂, MgSO₄, Na₂SO₄, lactose, and whole milk. The manufacturing route corresponds to the standard method of production of quark, wherein merely a retentate from a nanofiltration step of whole milk is used, instead of using skimmed milk within the meaning of the present application [cf. LAIT VOL. 80 (1), p 43-50 (2000)].

In DEUTSCHE MILCHWIRTSCHAFT VOL 48(2), p 36-41(1997), a process for the production of fresh cheese is disclosed, wherein skimmed milk is concentrated by means of nanofiltration. The milk is subsequently heated at a temperature of 80° C. for seven minutes, is subsequently stirred into a selected combination of cultures at 30° C., and is then allowed to ferment for 14 to 16 hours. After fermentation, the desired dry matter content of the final product is adjusted by ultrafiltration or separation.

EP 1364582 A1 relates to an acidified dairy product having milk and/or skimmed milk and/or whey as its main component. Specifically, acidified dairy products are claimed, which are obtained by removal of monovalent ions and water by means of nanofiltration from the primary dairy products and/or whey products.

A particular problem in the context of the production of fresh cheese is producing matrices that have a neutral taste. When skimmed milk is pre-concentrated by means of ultrafiltration in order to form a quark matrix, which is subsequently acidified, the product has a very bitter taste and is not acceptable from a sensory perspective. This sensory deviation is particularly induced by the presence of bitter proteins and phosphates. Alkali metal ions, particularly sodium, tend to cause a metallic taste. The methods for concentrating non-acidified skimmed milk to obtain quark of the state of the art have not been capable of quantitatively separating phosphates and alkali metal ions yet, with amounts thereof remaining in the product such that an adverse taste cannot be prevented.

Further, acid whey is generated in the conventional production of quark as a by-product, which is complex to remove from the curd and which only has limited possibilities of use.

One way to improve the taste properties is in the use of particular starter cultures which contribute to masking the perception of a bitter taste (cf. EP 2839748, EP 2839749 A1, DMK), which, however, does not change any of the presence of those bitter principles—and which certainly does not solve the problem of the by-product of acid whey. If it is intended to factually separate the bitter principles—also against the background of low-sodium products—there must be another way.

For example, in order to improve the taste quality of fresh cheese or quark, EP 2796051 A1 (DMK) suggests to initially subject skimmed milk to a coupled ultrafiltration and nanofiltration, subjecting the permeate thus obtained to demineralisation as a result of a precipitation reaction, and to combine the low-mineral filtrate with the high-protein retentate from the ultrafiltration step before denaturing, fermenting, and standardising this mixture. This process, however, has a disadvantage in that neither the separation of bitter principles nor of monovalent cations, specifically sodium, that cause a metallic aftertaste, is performed completely and the resulting product thus is not of a suitable taste. In addition, the precipitation of the calcium salts is technically complex and quite expensive.

The object of the present invention was therefore to provide a quark matrix having an improved taste and a reduced portion of bitter principles, specifically bitter proteins, and a reduced sodium content (below 50 ppm, preferably below 10 ppm) and improved sensory and taste properties at the same time, specifically with regard to the teaching of EP 2796051 A1 stated above, which is ready to fill and ready to eat without the addition of additives. Simultaneously, it should be possible to perform the corresponding method of production without that acid whey is produced as a waste by-product, providing by-products having a higher value instead.

DESCRIPTION OF THE INVENTION

A first subject matter of the invention relates to a quark matrix having improved taste characteristics, which is obtainable or obtained by

-   (a) subjecting raw milk to heat treatment, separating the cream, -   (b) subjecting the skimmed milk such obtained to an ultrafiltration     step, a microfiltration step, and/or a reverse osmosis step,     obtaining a high-protein retentate R1 and a high-lactose permeate P1     in the process, -   (c) enriching the retentate with an amount of lactose which     corresponds to the amount that had been separated as permeate in the     ultrafiltration step before, -   (d) subjecting the enrichment product such obtained to heat     treatment until denaturation sets in, -   (e) fermenting the denaturation product such obtained by the     addition of starter cultures and rennet, and -   (f) adjusting the fermentation product such obtained to defined dry     matter and protein contents.

In particular, an amount of lactose is added to the retentate in step (c), the protein content of which is above the target value of the quark with regard to its composition, as a result of which quark will be present directly after the fermentation step. The person skilled in the art can easily determine the required amounts due to their general specialist knowledge. Thus, this process can be applied to other varieties of fresh cheese and is not limited to quark only, a typical German product.

Another subject matter of the present invention is a corresponding process for the production of a corresponding quark matrix, comprising the following steps:

(a) producing a skimmed milk by heat treatment of raw milk and separation of the cream;

(b) subjecting the skimmed milk such obtained to an ultrafiltration step, a microfiltration step, and/or a reverse osmosis step, obtaining a high-protein retentate R1 and a high-lactose permeate P1;

(c) enriching the retentate with an amount of lactose which corresponds to the amount that had been separated in the ultrafiltration step as permeate before,

(d) subjecting the enrichment product such obtained to heat treatment until denaturation sets in,

(e) fermenting the denaturation product such obtained by the addition of starter cultures and rennet, and

(f) adjusting the fermentation product such obtained to defined dry matter and protein contents.

Surprisingly, it was found that the object of the invention was completely achieved by merely subjecting skimmed milk to an ultrafiltration step and/or a microfiltration (or reverse osmosis) step and subsequently enriching the retentate obtained, which contains the valuable long-chain taste-neutral proteins, with lactose until the original value is achieved, which is then processed.

It is of a particular advantage that a second high-protein phase is obtained as permeate, which is a valuable by-product, practically containing all short-chain bitter proteins along with lactose, and which may be processed separately (WPC=whey protein concentrate).

In contrast to a combination of ultrafiltration, nanofiltration, and precipitation steps, the process of the invention proves to be technically less complex and is faster; with the permeate, also the largest part of the mineral salts is removed, leading to a lower sodium content and, simultaneously, to a further improved taste quality. The sodium values are typically within the range of 5 to 50 ppm.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will be described in greater detail with reference to the accompanying drawing which schematically illustrates the process according to the present invention compared to the prior art.

PRODUCTION OF SKIMMED MILK

In order to produce skimmed milk, a separation of non-dairy components and the skimming of the fat content of about 4% by weight from the raw milk is initially performed. This is usually carried out in a special component, preferably a separator. Said components are adequately known from the state of the art. Separators of the company GEA Westfalia Separator GmbH, which allow that these steps may be performed together or individually, are widely used in the dairy industry¹. Corresponding components have also been disclosed, for example, in DE 10036085 C1 (Westfalia) and are perfectly known to one skilled in the art. Therefore, no explanations are needed on how to carry out these process steps, as they are understood to be part of the general specialist knowledge. ¹(http://www.westfalia-separator.com/de/anwendungen/molkereitechnik/milch-molke.html).

Heat treatment of the raw milk is preferably carried out in heat exchangers, in which case, specifically, plate heat exchangers have proved to be particularly suitable. There is a temperature gradient at the heat exchangers, which, however, is selected such that the raw milk is heated to a temperature of about 70 to 80° C., and particularly of about 72 to 74° C. for a residence time of a minimum of 20 and a maximum of 60 seconds, preferably about 30 seconds.

Ultrafiltration, Microfiltration, and Reverse Osmosis

In the second process step, the skimmed milk is separated, by means of an ultrafiltration step, into a dairy protein concentrate, which is obtained as retentate, and a dairy permeate.

The term ultrafiltration describes a filtration through membranes having a pore size<0.1 μm (1,000 to 50,000 Dalton), while a filtration at pore sizes>0.1 μm is usually referred to as microfiltration. In both cases, this concerns purely physical, i.e., mechanical membrane separation methods which apply the principle of mechanical size exclusion: all particles in the fluids which are larger than the membrane pores are retained by the membrane. The driving force in both separation methods is the differential pressure between the inlet and the outlet of the filter area, which is between 0.1 and 10 bar. Depending on the area of application, the filter area material may consist of stainless steel, synthetic material, ceramics or textile fabric. Filter elements appear in different forms: candle filters, flat membranes, spiral coil modules, bag filters and hollow fibre modules, all of which are, in principle, suitable within the meaning of the present invention.

Ultrafiltration is preferably performed at temperatures within the range of about 10 to about 55, preferably about 10 to 20° C., with membranes preferably having an average pore size of 1,000 to about 50,000, more particularly about 5,000 to about 25,000 Dalton. Preferably, the membranes are so-called spiral coil modules or plate and frame modules made of polysulfone or polyethylene membranes.

Reverse osmosis represents an alternative to ultrafiltration. In this process, the skimmed milk is dehydrated using a semi-permeable membrane, increasing the concentration of the valuable dairy proteins as a result. The principle of the process is that the system is subjected to a pressure which must be higher than the pressure created by the osmotic pressure for concentration equilibration. As a result of this, the molecules of the solvent can migrate in the opposite direction to their “natural” osmotic spreading direction. The pressure forces them into the compartment in which dissolved substances are present in a less concentrated form. Milk has an osmotic pressure of less than 2 bar, the pressure applied for reverse osmosis of milk is 3 to 30 bar, depending on the membrane used and the configuration of the equipment. The osmotic membrane through which only the carrier liquid (solvent) is allowed to pass, retaining the dissolved substances (solutes), must be able to withstand these high pressures. In case the pressure difference more than balances the osmotic gradient, the molecules of the solvent are passing through the membrane just like in a filter, while the milk molecules are retained. In contrast to a classic membrane filter, osmotic membranes do not have through pores. Reverse osmosis is preferably performed at a temperature within the range of 10 to 55, more particularly 10 to 20° C. with semi-permeable membranes having a cut-off of 0 to 1,000 Dalton.

Adjusting the Lactose Content

In the course of ultrafiltration, a retentate is obtained, which contains the valuable long-chain taste-neutral proteins while the permeate contains lactose, salts, and short-chain bitter proteins; these can be treated separately. In order to obtain a pleasantly tasting quark matrix on the basis of the retentate, lactose is added to the same in an amount such that the original lactose content is reached. It is certainly also possible to adjust smaller amounts of lactose if it is intended to obtain low-lactose products. Typically, the retentate is adjusted to a lactose content of about 0.1 to about 3% by weight, preferably about 0.5 to about 2.5% by weight and particularly about 1 to about 2% by weight. If lactose is exchanged for a mixture of glucose and galactose having the same molecular mass, it is possible to produce lactose-free products.

It is also possible to use this process step in order to introduce other substances. Herein, the nature of these other additives is uncritical. Said additives may be other carbohydrates, for example, sugar, but also food additives such as lactoferrin or unsaturated fatty acids may be introduced.

Denaturation

In the following step, the high-protein fraction from the ultrafiltration step, i.e., the retentate, which was enriched with an amount of lactose as described above, is subjected to heat treatment. The denaturation now performed may be carried out by a method known in itself, namely, for a period of about 5 to about 10 min, and preferably about 6 min, and at temperatures of about 85 to about 90° C., more particularly about 88° C.

Fermentation and Standardisation

Also the fermentation of the denatured precursor can be performed according to the known methods of the state of the art. To this end, suitable starter cultures, preferably lactic acid bacteria, and rennet, are added. Suitable starter cultures are particularly probiotic bacteria of the type Bifido bacterium lactis B12 or Lactobacillus acidophilus as well as mesophilic bacteria such as, for example, Lactococcus lactis or Leuconostoc cremoris.

Further, the two following cultures are particularly preferred, which consist of 5 or 3 probiotic bacteria, namely:

Mixture 1

(i-1) Streptococcus thermophilus,

(i-2) Leuconostoc species,

(i-3) Lactococcus lactis subsp. lactis biovar diacetylactis,

(i-4) Lactococcus lactis subsp. lactis, and

(i-5) Lactococcus lactis subsp. cremoris, as well as

Mixture 2

(ii-1) Streptococcus thermophilus,

(ii-2) Lactococcus lactis subsp. lactis, and

(ii-3) Lactococcus lactis subsp. cremoris.

Preferably, the starter cultures contain

-   -   about 10 to about 90% by weight, preferably about 25 to about         75% by weight and more particularly about 40 to about 60% by         weight of mixture (i), and     -   about 90 to about 10% by weight, preferably about 75 to about         25% by weight and more particularly about 60 to about 40% by         weight of mixture (ii)         with the proviso that the quantities add up to 100% by weight.

Particularly preferred are starter cultures, containing

-   -   about 40 to about 60% by weight of mixture (i), and     -   about 60 to about 40% by weight of mixture (ii)         with the proviso that the quantities add up to 100% by weight.

In another preferred embodiment, the five microorganisms forming mixture (i) and the three microorganisms forming mixture (ii) are each contained in about the same quantities. “About the same” in this context is to be understood as meaning that in mixture (i) the five microorganisms are each contained in quantities of 20±5% by weight, and in mixture (ii) the three microorganisms are each contained in quantities of 33±5% by weight. Instead of employing the commercially available preparations (i) and (ii) together, it is, in principle, certainly also possible to use the five microorganisms individually, mixing them such that a mixture of starter cultures is obtained, by means of which the quark products having an improved taste are obtained. Those starter cultures preferably contain

-   -   about 20 to about 30% by weight Streptococcus thermophilus,     -   about 5 to about 15% by weight Leuconostoc species,     -   about 5 to about 10% by weight Lactococcus lactis subsp. lactis         biovar diacetylactis,     -   about 20 to about 30% by weight Lactococcus lactis subsp.         lactis,     -   about 20 to about 30% by weight Lactococcus lactis subsp.         cremoris, and with the proviso that the quantities add up to         100% by weight.         Particularly preferred are starter cultures, containing     -   25% by weight Streptococcus thermophilus,     -   12% by weight Leuconostoc species,     -   13% by weight Lactococcus lactis subsp. lactis biovar         diacetylactis,     -   25% by weight Lactococcus lactis subsp. lactis,     -   25% by weight Lactococcus lactis subsp. cremoris

All microorganisms mentioned are commercially available.

The temperature at which fermentation is performed depends on the range of temperature which is optimal for the microorganisms used in each case; typically, the temperature is within the range of about 18 to about 35° C., and preferably at about 30° C.

The quark matrix obtained after fermentation is subsequently adjusted to the desired dry matter and protein contents, for example, by the addition of cream (about the fraction obtained during the production of the skimmed milk). Preferably, the dry matter content is about 15 to about 20% by weight, and more particularly about 18% by weight. The protein content may be about 10 to about 15% by weight, and preferably about 12% by weight.

INDUSTRIAL APPLICABILITY

A further subject matter of the present invention relates to foods, containing the quark matrices according to the invention. This is to be understood as meaning that the matrices themselves represent a component of the food, for example, of a fresh cheese preparation or a quark dish, or are used as an ingredient in the process of the production of the food, for example, in the production of quark (cheese) cake.

EXAMPLES Comparison Example V1

4,000 kg skimmed milk were treated at 88° C. for 6 min, denaturing the proteins obtained. Lactic acid bacteria according to mixture (i) and rennet were added to the matrix, which was allowed to ripen at 30° C. for about 18 h and subsequently stirred. Subsequently, the fermentation product was placed into a centrifuge, separating ca. 3.2 kg acid whey as a liquid component. The remaining quark matrix (ca. 800 kg) was adjusted to a fat content of 40% by weight in the dry matter and a protein content of 12% by weight by adding cream.

Comparison Example V2 (Analogous to EP 2796051 A1

4,000 kg skimmed milk were subjected to an ultrafiltration step using a spiral coil membrane (cut-off 25,000 Dalton) at 20° C. The high-protein retentate was separated, and the permeate was subjected to a nanofiltration step using a spiral coil membrane at 20° C. (cut-off 500 Dalton). Sodium salts and potassium salts were separated along with the permeate. Subsequently, the retentate was treated by adding an aqueous calcium chloride solution that had been adjusted to pH=6 using NaOH, precipitating the phosphates as calcium phosphate. The permeate such obtained was combined with the high-protein retentate from the first step, it was treated at 88° C. for 6 min, denaturing the proteins contained therein. Lactic acid bacteria according to mixture (i) and rennet were added to the matrix, which was stirred at 30° C. for about 2 h. Subsequently, the fermentation product was placed into a centrifuge, separating the acid whey as a liquid component. The remaining quark matrix was adjusted to a fat content of 40% by weight in the dry matter and a protein content of 12% by weight by adding cream.

Example 1

4,000 kg skimmed milk were subjected to an ultrafiltration step using a spiral coil membrane (cut-off 25,000 Dalton) at 20° C. The high-protein retentate was separated, and the permeate, which contained short-chain bitter proteins along with lactose, was processed separately. The retentate was adjusted to its original content of 2.8% by weight using lactose such that quark was obtained directly after the fermentation step, and the enrichment product such obtained was subsequently treated at 88° C. for 6 min, denaturing the proteins contained therein. Lactic acid bacteria according to mixture (i) and rennet were added to the matrix, which was stirred at 30° C. for about 2 h. Subsequently, the fermentation product was placed into a centrifuge, separating the acid whey as a liquid component. The remaining quark matrix was adjusted to a fat content of 40% by weight in the dry matter and a protein content of 12% by weight by adding cream.

Tasting

The quark matrices were stored in a refrigerator at 10° C. for 24 hours, were subsequently allowed to adapt to environment temperature for 5 minutes, and were then evaluated by 5 assessors for their taste and sensory properties, wherein the scale ranged from (1)=“weakly present” to (5)=“very pronounced”. In addition, the sodium content of the products was determined. The results are summarised in Table 1. The average values of the tasting are indicated. Example 1 is according to the invention, examples V1 and V2 are for comparison purposes.

TABLE 1 Results of the tasting V1 V2 1 Taste evaluation bitter 4.0 2.5 1.0 grainy 4.0 2.5 1.5 fresh 2.0 4.0 4.0 Sensory evaluation creamy 2.5 4.0 4.0 soft 2.5 4.0 4.0 Sodium content Not determined 145 28 [ppm] In comparison with the closest state of the art, the product according to the invention is not only characterised in that it has a sodium content that is reduced by more than ¾, but it is also perceived to be less bitter and less grainy during the tasting, and tends to be more fresh and more creamy.

In the following, the processes according to examples 1 as well as V1 and V2 are schematically explained in FIG. 1. Here, the abbreviations have the following meaning:

T=Heat treatment (denaturation)

FM=Fermentation

SP=Separation

ST=Standardisation

UF=Ultrafiltration

DM=Demineralisation

MX=Mixing 

The invention claimed is:
 1. A process for the production of a low-mineral quark matrix, comprising the combination of the following order of steps of: (a) producing a skimmed milk by heat treatment of raw milk, and separation of cream; (b) subjecting the skimmed milk such obtained to an ultrafiltration step, with a membrane having a cut-off of 1,000 to 50,000 Dalton, obtaining a high-protein retentate R1 and a high-lactose permeate P1; (c) enriching the retentate R1 with an amount of lactose which corresponds to an amount separated in the ultrafiltration step as permeate, and which is not the permeate P1 removed in step (b), (d) heat treating an enrichment product such obtained until denaturation sets in, (e) fermenting a denaturation product such obtained by adding starter cultures and rennet, and (f) adjusting a fermentation product thus obtained to defined dry matter and protein content, wherein a quark matrix having both reduced sodium content and improved sensory taste properties being less bitter, less grainy, more fresh, more creamy and softer, is obtained.
 2. The process of claim 1, wherein the ultrafiltration is performed using spiral coil modules and/or plate and frame modules.
 3. The process of claim 1, wherein the ultrafiltration is performed at a temperature within the range of 10 to 55° C.
 4. The process of claim 1, wherein the enrichment product is adjusted to a lactose concentration of about 0.1 to about 3% by weight.
 5. The process of claim 1, wherein further additives are added to the enrichment product.
 6. The process of claim 1, wherein the enrichment product of the retentate R1 and lactose is subjected to heat treatment at a temperature of 85 to 90° C. for a period of 5 to 10 minutes, and denaturing.
 7. The process of claim 1, wherein the cultures and rennet are added to the denaturation product at 25 to 35° C.
 8. The process of claim 1, wherein the cultures are one of the two following mixtures 1 or 2: Mixture 1 (i-1) Streptococcus thermophilus, (i-2) Leuconostoc species, (i-3) Lactococcus lactis subsp. lactis biovar diacetylactis, (i-4) Lactococcus lactis subsp. Lactis, and (i-5) Lactococcus lactis subsp. cremoris, and Mixture 2 (ii-1) Streptococcus thermophilus, (ii-2) Lactococcus lactis subsp. lactis, and (ii-3) Lactococcus lactis subsp. cremoris.
 9. The process of claim 1, wherein the fermentation product is adjusted to a dry matter content of 15 to 20% by weight and a protein content of 10 to 15% by weight.
 10. The process of claim 1, wherein the fermentation product is adjusted by adding a portion of the cream fraction from step (a).
 11. The process of claim 1, comprising the additional step of (g) separately processing the permeate P1 obtained in step (b) and which practically contains all short-chain bitter proteins along with lactose.
 12. The process of claim 4, wherein the enrichment product is adjusted to a lactose concentration of about 0.5 to about 2.5% by weight.
 13. The process of claim 12, wherein the enrichment product is adjusted to a lactose concentration of about 1 to about 2% by weight.
 14. The process of claim 1, wherein a quark matrix having a sodium content below 50 ppm is obtained. 